[Bug] Blaze: hidden html attribute does not work properly

[gcacars]

Blaze dynamic attributes doesn't work properly with attribute hidden.

If you use:

helperName(){
    return {
        checked: false
}

It works great, removing the checked attribute.
But when you use:

helperName(){
    return {
        hidden: false
}

Blaze creates a html with:

hidden="false"

that occurs in an hidden element.

[mitar]

Probably it just has to be added here: https://github.com/meteor/blaze/blob/master/packages/blaze/attrs.js#L296

This could be a simple pull request. Would you like to contribute it?

Also, there are probably some other new HTML5 attributes likes that.

[mitar]

A different fix has been implemented in 84c58a6.